1. Field of the Invention
The present invention relates to wireless communication and, more particularly, to a method and apparatus for adjusting a power control mode in a wireless communication system.
2. Related Art
The next-generation multimedia wireless communication systems that are being actively researched in recent years are required to process various pieces of information, such as video and wireless data, at a higher data transmission rate as well as the initial voice-centered services.
In the case of broadband wireless communication systems, effective transmission and reception schemes and their application methods have been proposed in order to maximize the efficiency of limited radio resources. One of systems that are being taken into consideration, from among the next-generation wireless communication systems, is an Orthogonal Frequency Division Multiplexing (OFDM) system capable of attenuating an Inter-Symbol Interference (ISI) effect with a low complexity. In the OFDM system, data symbols received in series are converted into an N number of parallel data symbols and then transmitted with them carried on an N number of respective separated subcarriers. The subcarriers maintain orthogonality in the frequency dimension. Each of orthogonal channels experiences independent frequency selective fading. Accordingly, the degree of complexity at a reception stage is reduced and the gap between the transmitted symbols is lengthened, thereby being capable of minimizing ISI.
Orthogonal Frequency Division Multiple Access (OFDMA) refers to a multiple access method of realizing multi-access by independently providing users with some of available subcarriers in a system using OFDM as a modulation method. In general, in the OFDMA method, frequency resources called subcarriers are provided to each user, and frequency resources are independently provided to a number of respective users such that they do not overlap with each other. Consequently, the frequency resources are exclusively assigned to the respective users. In an OFDMA system, frequency diversity for multiple users can be obtained through frequency selective scheduling, and subcarriers can be assigned to the users in various ways according to a permutation method for the subcarriers. Further, the efficiency of a space domain can be increased through a space multiplexing scheme using multiple antennas.
A wireless communication system uses a power control scheme as one of methods for reducing a path loss according to the distance between a base station and a terminal and Inter-Cell Interference (ICI) resulting from neighbor cells. The power control scheme is a scheme for adjusting transmission power such that data can be transmitted at the lowest power level while maintaining the Quality of Service (QoS) of a wireless communication system. In particular, in multi-cell environments, terminals near a cell boundary are greatly influenced by a path loss, ICI, etc. The terminals must determine proper transmission power and transmit data such that the QoS is not deteriorated according to a path loss while not interfering with neighbor cells.
Accordingly, there is a need for an effective power control scheme for an efficient system.